"You're right next to some tall buildings, they cause GPS reflections and large position errors. A 3D fix doesn't mean it's going to be accurate when you're around tall buildings, it just means you're tracking 4+ strong satellites. You can try going…"

"Having more satellites would almost always help you in terms of HDOP. You'd have twice as many satellites and HDOP represents the spread of the satellite geometry in the sky. If you have a limited view if the sky you'd still see more satellites…"

"This is the backup battery which allows the module memory to be saved. When you have the backup battery you will begin with a hot start (or warm start depending on how long it's been) instead of a cold start. A hot start will give you a position fix…"

"When I've seen this sort of stuff it's been a loose connection in the cable. Maybe it's being powered on and off with a faulty connection. The GPS modules wouldn't do this if they were continuously powered and connected.  "

"If you want to use RTL then you need a good position to begin with. If you have a HDOP above 2 you could have position errors of 20m+ at your home location. When you began to fly the HDOP will get better, but that original position would still be…"

"The signal to noise ratio and jamming indicator could help you setting up your drone to make sure there isn't interference from something internally. Take a baseline measurement with the GPS antenna in open sky and away from everything, then place…"

"The default settings should work well, so nothing needs to be changed. If you do change the configuration in u-center then you have to save it with >Receiver>Action>Save Config or it will be erased when you power off. 
You can change the…"